Screening and Optimization of Polyhydroxybutyrate Production by Streptomyces sp. 3MGH Isolated from the Egyptian Soil

The increasing dependence on non-biodegradable plastics poses significant environmental challenges, driving the need for sustainable alternatives like polyhydroxybutyrate (PHB). This study aimed to isolate and optimize PHB production from Streptomyces sp. 3MGH, a bacterium isolated from Egyptian soil. Soil samples were collected from various locations, leading to the isolation of 25 Streptomyces species. Qualitative screening using Sudan Black B staining identified 14 PHB-producing isolates. Among these, Streptomyces sp. 3MGH demonstrated the highest PHB yield of 3.34 g/L. Molecular identification via 16S rRNA sequencing confirmed its close phylogenetic relationship to known Streptomyces strains. Optimization experiments evaluated the effects of carbon and nitrogen sources, incubation temperature, time, and shaking speed on PHB production. The results indicated that optimal conditions for PHB accumulation were achieved at an incubation temperature of 30 °C, with 150 rpm agitation, and a 7-day incubation period using fructose as carbon source and yeast extract as nitrogen source. These findings suggest that Streptomyces sp. 3MGH presents significant potential for industrial-scale PHB production, contributing to the development of biodegradable plastics.